fix up read the docs

.readthedocs.yaml

@@ -5,19 +5,17 @@
 # Required
 version: 2
 
-# Set the OS, Python version and other tools you might need
+# Build documentation in the "docs/" directory with Sphinx
+sphinx:
+  configuration: docs/source/conf.py
+  builder: html
+
 build:
   os: ubuntu-22.04
   tools:
     python: "3.12"
     rust: "1.64"
 
-# Build documentation in the "docs/" directory with Sphinx
-sphinx:
-  configuration: docs/source/conf.py
-
-# Optional but recommended, declare the Python requirements required
-# to build your documentation
 # See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
 python:
     install: